To be honest, I don't know how much help you'll get at this forum. There are a few knowledgeable people here in regard to acoustics and recording and all that, but I don't know if any of us have ever actually built a full-on studio.
While I could give plenty tips, as far as construction from the ground up, that might be better suited for those who have done it.
I did a search and found this forum that might be right on the money for you, and it's pretty active:
John Sayers' Recording Studio Design Forum • Index page
Check out the studio design subforum to get ideas, and you might want to sign up there and post your room so others there can have a stab at coming up with some layouts. Good luck!